1. Field of the Invention
The present invention relates to a sliding bearing and a rotating and sliding member, and more specifically, to a sliding bearing and a rotating and sliding member, wherein disadvantages are difficult to be arisen due to the rotation of a shaft and a sliding portion at a high speed.
2. Description of the Related Art
Conventionally, sliding bearings are used in various applications, such as a bearing adapted to support various rollers in a toner unit and a fixing unit in a duplicator, a laser beam printer and the like, a bearing used in a micro-motor and the like.
A conventional example of such a type of a sliding bearing is shown in FIG. 1. The bearing 10 is made by an injection molding process using, for example, a synthetic resin as a starting material, and mounted in a fixed state on a base plate (not shown) or the like on a unit body. The sliding bearing 10 has an inner peripheral surface 11 formed of a side of a cylindrical hole defined in correspondence to an external shape (a columnar shape) of a rotary shaft 12.
The rotary shaft 12 used in this type of the sliding bearing 10 is formed, for example, into a columnar rod-shape, and inserted through the hole defined in the sliding bearing 10 and rotatably supported therein. A gear (not shown) is mounted on the rotary shaft 12, so that a rotating force is transmitted from a power source by bringing the gear into meshing engagement with another gear (not shown).
The rotary shaft 12 is formed, so that its side portion other than a portion supported on the sliding bearing 10 is brought into contact with a side of a rotatable cylindrical member (not shown). Thus, a printer paper clamped between the rotatable cylindrical member and the rotary shaft 12 can be fed by rotating the rotatable cylindrical member and the rotary shaft 12.
Moreover, such conventional sliding bearing is formed, so that an area of an inner peripheral surface extending between axial opposite ends is brought into sliding contact with the rotary shaft, leading to an increased area of contact with the rotary shaft. Therefore, the friction on the rotation of the rotary shaft is larger, and when the rotary shaft is rotated at a high speed, the temperature of the rotary shaft is liable to be risen. Moreover, since the area of the inner peripheral surface extending between the axial opposite ends is brought into sliding contact with the rotary shaft, a heat generated at the sliding-contact portion is difficult to escape to the outside. As a result, the siding bearing is liable to be thermally expanded largely and hence, the expansion and deformation of the sliding bearing tend to exert an adverse influence to the rotational accuracy of the rotary shaft. In addition, the wearing of the inner peripheral surface of the sliding bearing due to the friction is liable to be advanced early. For this reason, if the conventional sliding bearing is used as it is, for example, as a bearing for supporting any of various rollers used in a printer or the like in which an increase in printing speed has been demanded in recent years, there is a possibility that an adverse influence is exerted to the quality and life of a product, for example, it is difficult to maintain the rotational accuracy of the rotary shaft over a long period.
In a rotating and sliding member such as a gear and a pulley rotatably supported on a shaft, in addition to the above-described sliding bearing, there is also a possibility that an adverse influence is exerted to the rotational accuracy of the rotary shaft, the life of a product and the like due to the increase in rotational speed.
Accordingly, it is an object of the present invention to provide a sliding bearing and a rotating and sliding member, wherein disadvantages such as the accumulation of a heat and the wearing can be suppressed to maintain a high rotational accuracy over a long period and to prolong the life of a product.
To achieve the above object, according to the present invention, there is provided a sliding bearing for rotatably supporting a rotary shaft, comprising a projection formed on at least a portion of its surface opposed to the rotary shaft.
In the sliding bearing according to the present invention, the projection may be formed in a direction of rotation of the rotary shaft.
In the sliding bearing according to the present invention, the projection may be formed in a direction intersecting a direction of rotation of the rotary shaft.
According to the present invention, there is provided a rotating and sliding member rotatably supported on a shaft, comprising a projection formed on at least a portion of its surface opposed to the shaft.
In the sliding bearing according to the present invention, the projection may be formed in a rotating direction.
In the sliding bearing according to the present invention, the projection may be formed in a direction intersecting a rotating direction.
With the sliding bearing according to the present invention, the area of contact with the rotary shaft can be reduced to reduce the friction force. Therefore, even if the rotary shaft is rotated at a high speed, the frictional heat can be reduced to suppress the thermal expansion of the bearing, leading an enhanced rotational accuracy of the rotary shaft. In addition, the degree of progress of the wearing can be suppressed by the reduction in friction force, thereby enhancing the endurance to prolong the life of a product.
Further, when such configuration of the sliding bearing is applied to a rotating and sliding member, an effect similar to that of the sliding bearing can be provided.